Field of the Invention
The present invention relates to an image forming system.
Description of the Related Art
An image forming apparatus using an electrophotographic system is known. The image forming apparatus of this type forms an image on a sheet by executing a series of processes such as image transfer and image fixation. With increasing variations of needs from users, there is a demand for such an image forming apparatus capable of handling a job designating a different sheet type for particular pages in a series of pages, as well as a job designating the same sheet type for the respective pages constituting the job.
A fixing control temperature set for an image forming apparatus varies according to a paper type (sheet type). Accordingly, a setting value of the fixing control temperature needs to vary in accordance with switching of the sheet type at the time of execution of a job handling a mixture of plural sheet types. Switching of the fixing control temperature requires a certain period of time, and thus increases a processing time for executing one job. The productivity tends to lower as the processing time increases.
A possible solution to this problem is to unify respective sheets into groups of sheet types each having the same fixing control temperature, and perform printing for each sheet type. In this case, a switching frequency of the fixing control temperature decreases in comparison with printing performed in the page order. Accordingly, productivity is expected to improve.
For example, JP 2003-280461 A discloses an image forming apparatus which unifies respective sheets into groups of sheet types, and outputs the respective sheet types in the ascending order of the fixing control temperature when different sheet types are designated for a plurality of images formed on sheets.
On the other hand, JP 2011-73246 A discloses a printing device. More specifically, the printing device temporarily determines the printing order such that printing starts in the descending order of drying time for images with reference to a printing table created in response to a printing instruction designating a plurality of images and a discharge order of these images. The printing device allocates the respective images to four drying stages such that the difference in the sum of the drying time becomes the minimum between the respective drying stages. The printing device sorts the temporarily determined printing order such that the front-rear relationship between the images allocated to each drying stage becomes identical to the front-rear relationship of the discharge order to determine the printing order. The printing device prints images in accordance with the determined printing order, distributes the printed sheets to the respective drying stages, and discharges the distributed sheets from the respective drying stages in accordance with the discharge order.
When printing is performed for each sheet type, however, the output order changes from the page order designated by the job. Accordingly, there is a necessity for executing a process for inserting the earlier printed sheet type between pages of the subsequently printed sheet type to arrange the respective sheets in the designated page order. This process is considerably complicated particularly when the process is manually executed. The complication of the process becomes more remarkable as the number of pages and the number of copies increase. Furthermore, in case of a series of devices (image forming system) constituted by an image forming apparatus and devices provided downstream, this process requires sufficient consideration about elements, such as a page configuration of a job and configurations of the downstream devices, as elements conceivable in various possible modes. When sufficient consideration is not made, work efficiency and productivity may lower.